A sextant is a doubly reflecting navigation instrument used to measure an angle between two visible objects. The primary use of the sextant is to determine the angle between an astronomical object (e.g., the sun, the moon, stars) and the horizon (or skyline) for the purposes of celestial navigation. The determination of the angle, or altitude, can be referred to as sighting the object. The angle, in addition to the time at which the angle is measured, can be used to calculate a position line on a nautical or aeronautical chart. A sextant can be commonly used to sight the sun or other stars to determine latitude. In addition, the sextant can be used to measure the lunar distance between the moon and another celestial object (e.g., a star or planet) in order to determine Greenwich Mean Time, and hence longitude.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.